docs: def _Ep(self):
          """ Proton energy array in GeV
          """
          return np.logspace(
              np.log10(self.Epmin.to("GeV").value),
              np.log10(self.Epmax.to("GeV").value),
              int(self.nEpd * (np.log10(self.Epmax / self.Epmin))),
          )